Existing cockpit air conditioning systems provided for small aircraft such as military fighter or trainer aircraft are supplied with air which is bled from the aircraft engine. The air is passed through a heat exchanger to be cooled and then circulated around the cockpit, under pressure, through supply pipes on each side of the pilot's seat. Apertures in the supply pipe allow the air to escape and circulate inside the cockpit. The apertures usually contain controllable ventilation nozzles which are positioned so as to be within easy reach of the seated pilot and to enable him to direct and adjust the flow of air for maximum comfort within the cockpit. The ventilation nozzles presently used are of a type which comprise a series of louvres of vanes rotatably mounted within each aperture in the air supply pipe. The louvres are angled to deflect the air in a chosen direction as it passes through them. The whole louvre assembly is fixed within a retaining ring rotatably mounted on the circumference of the aperture so that by rotating the ring clockwise or anti-clockwise the pilot is able to direct the air flow. In addition the nozzle usually has a flow control valve mounted in it which enables the pilot to alter the volume and rate of air flow through the louvres. The flow control valve usually comprises a disc which obstructs the air flow through the vent by an amount depending on the position of the disc within the vent. The position of the disc is adjustable by a separate rotatable knob provided in the centre of the nozzle which may be rotated independently of the rotation of the louvre assembly.
A drawback with such louvre systems is that they are expensive to manufacture even by moulding techniques as they may be made from as many as nine separate components all of which require individual manufacture.
Apart from the cost and complexity of manufacturing the present nozzles they tend to be unreliable in operation. One problem is that they are prone to variable frictional forces around the edge of the vent making it difficult to maintain the louvre assembly in the required position. Sometimes the louvre assemblies move round of their own accord due to aircraft vibration and the pilot has to continually re-adjust them which is tedious from the pilot's point of view. Furthermore, the rotatable knob controlling the air control valve protrudes into the cockpit and can sometimes catch in the pilot's clothing and restrict his movements which could obviously be awkward or dangerous particularly if the pilot's concentration is distracted during a manoeuvre.
Ventilation nozzles for road vehicles are known, e.g. from British Patent Nos. 743 236; 768 139; 826 791 and 1 376 302 and from U.S. Pat. Nos. 3,814,001 and 4,524,679; such nozzles have a spherical ball provided with air passageways therethrough and the ball if fixed in a part-spherical retaining socket in the manner of a ball-and-socket joint so that the ball can be rotated within the socket to direct air in any desired direction. However, the ball and/or the socket can become worn through use thereby reducing the friction between the ball and the socket which results in the ball being held slackly by the socket and vibration can cause the ball to slip out of its desired orientation requiring continual re-adjustment. More seriously, however, the member can seize in the retaining socket, e.g. through the accumulation of dirt or through scuffing of the ball and/or the socket and when this occurs the member cannot be rotated at all (or can only be rotated with difficulty).
It is an object of the present invention to provide an air flow control nozzle that overcomes the above problems and which is simple in construction and cheap to manufacture. It is a further object of the present invention to provide an air flow control nozzle which is compatible with existing aircraft ventilation systems and which can be readily retrofitted to these with little or no modification thereto.